The University Group Diabetes Program (UGDP) was undertaken for the purpose of evaluating the effect of hypoglycemic treatment on the rate of development of vascular complications in mild adult-onset-diabetics. This is a multiclinic study involving 12 Clinical Centers and a Coordinating Center. Patients recruitment in this study started in February 1961 and was completed in early 1966 after a total of 1,027 patients had been enrolled. Patients were randomly assigned to one of the following treatment groups: insulin given in a fixed dose, insulin given in variable doses to maintain blood glucose levels within a normal range, tolbutamide, phenformin, or placebo. All patients were placed on diets designed to achieve or to maintain normal body weight. Information obtained from this study was used to evaluate the efficacy of treatments under study in preventing or delaying the onset and development of vascular complications in mild diabetics and to provide detailed information on the natural history of diabetes. Patient follow-up for the UGDP terminated in August 1975. The purpose of this application is to request support for the Coordinating Center to complete data analyses, to prepare the scientific reports for this study, and to prepare UGDP data for deposit in a central data repository.